Dear EarthTalk: Is it true that American kids are going through puberty earlier today than in previous generations, and are there any environmental causes for this?
-- Paul Chase
Research indicates that indeed Americans girls and boys are going through puberty earlier than ever, though the reasons are unclear. Many believe our widespread exposure to synthetic chemicals is at least partly to blame, but it's hard to pinpoint exactly why our bodies react in certain ways to various environmental stimuli.
Researchers first noticed the earlier onset of puberty in the late 1990s, and recent studies confirm the mysterious public health trend. A 2012 analysis by the U.S. Centers for Disease Control and Prevention (CDC) found that American girls exposed to high levels of common household chemicals had their first periods seven months earlier than those with lower exposures. "This study adds to the growing body of scientific research that exposure to environmental chemicals may be associated with early puberty," says Danielle Buttke, a researcher at CDC and lead author on the study. Buttke found that the age when a girl has her first period (menarche) has fallen over the past century from an average of age 16-17 to age 12-13.
Earlier puberty isn't just for girls. In 2012 researchers from the American Academy of Pediatrics (AAP) surveyed data on 4,100 boys from 144 pediatric practices in 41 states and found a similar trend: American boys are reaching puberty six months to two years earlier than just a few decades ago. African-American boys are starting the earliest, at around age nine, while Caucasian and Hispanics start on average at age 10.
One culprit could be rising obesity rates. Researchers believe that puberty (at least for girls) may be triggered in part by the body building up sufficient reserves of fat tissue, signaling fitness for reproductive capabilities. Clinical pediatrician Robert Lustig of Benioff Children's Hospital in San Francisco reports that obese girls have higher levels of the hormone leptin which in and of itself can lead to early puberty while setting off a domino effect of more weight gain and faster overall physical maturation.
Some evidence suggests that "hormone disrupting" chemicals may also trigger changes prematurely.
Public health advocates have been concerned, for example, about the omnipresence of Bisphenol A (BPA), a synthetic chemical in some plastics, because it is thought to "mimic" estrogen in the body and in some cases contribute to or cause health problems. BPA is being phased out of many consumer items, but hundreds of other potentially hormone disrupting chemicals are still in widespread use.
Dichlorobenzene, used in some mothballs and in solid blocks of toilet bowl and air deodorizers, is also a key suspect in triggering early puberty. It is already classified as a possible human carcinogen, and studies have linked prenatal exposure to it with low birth weight in boys. The U.S. Environmental Protection Agency (EPA) has recently made screening Dichlorobenzene for hormonal effects a priority.
Parents can take steps to reduce our kids' so-called "toxic burden": Buy organic produce, hormone- and antibiotic-free meat and dairy and all-natural household cleaners. And keep the dialogue going about healthy food and lifestyle habits so kids learn how to make responsible, healthy choices for themselves.
Dear EarthTalk: Why was the Colorado River named the most endangered river of 2013?
American Rivers, a leading non-profit dedicated to the conservation of rivers and riparian corridors across the U.S., recently unveiled its annual list of the nation's most endangered rivers.
The mighty Colorado earned the #1 spot, thanks mostly to outdated water management practices in the face of growing demand and persistent drought.
"This year's America's Most Endangered Rivers report underscores the problems that arise for communities and the environment when we drain too much water out of rivers," said American Rivers' president Bob Irvin. "The Colorado River...is so over-tapped that it dries up to a trickle before reaching the sea."
Indeed, 36 million of us drink water from the Colorado. The river responsible for cutting the Grand Canyon irrigates nearly four million acres of farmland where some 15 percent of the nation's crops are grown.
But according to American Rivers, over-allocation and drought have placed significant stress on water supplies and river health--and another summer drought is on the way.
A 2013 study by the federal Bureau of Reclamation finds that there isn't enough water in the Colorado to meet current demands and that the flow will be as much as 30 percent less by 2050 due to climate change. That reduced flow threatens not only endangered fish and wildlife but also the river system's $26 billion recreation economy.
"We simply cannot continue with status quo water management," said Irvin. "It is time for stakeholders across the Colorado Basin to come together around solutions to ensure reliable water supplies and a healthy river for future generations."
American Rivers has gathered dozens of community groups and other partners together to urge Congress to allot significant funds for river clean-up, state-of-the-art water conservation techniques in cities and on farms, and water sharing mechanisms that allow communities to adapt to warmer temperatures and more erratic precipitation as global warming takes effect.
Individuals can do their part by conserving water and spreading the word among friends and neighbors.
Another way to help is to send a letter to Congress via American Rivers' website outlining why instituting better water management practices up and down the Colorado is important to all Americans.
Meanwhile, National Geographic's Change the Course campaign challenges everyday Americans to pledge to shrink their "water footprint." For every pledge received, corporate sponsors donate funds that partnering orgnizations then use for ecological restoration and other projects that return water to the river.
The Colorado is far from the only U.S. river in trouble.
The runner-up on American Rivers' 2013 list is Georgia's Flint River, where excessive agricultural and municipal demands are taking too much water out.
The story is similar for several other rivers on the list: Texas' San Saba, Wisconsin's Little Plover, and the Catawba in North and South Carolina.
"The annual America's Most Endangered Rivers report is a list of rivers at a crossroads, where key decisions in the coming months will determine the rivers' fates," reported the group. "Over the years, the report has helped spur many successes including the removal of outdated dams, the protection of rivers with Wild and Scenic designations, and the prevention of harmful development and pollution."
The group hopes that all the attention it is showering on the Colorado this year will help turn it into another American conservation success story.
EarthTalk is written and edited by Roddy Scheer and Doug Moss and is a registered trademark of E -- The Environmental Magazine (www.emagazine.com). Send questions to email@example.com.